The invention relates in general to testing the functioning of radio apparatus. In particular the invention relates to testing the functioning of a digital radio apparatus on the basis of error statistics. The description of the invention especially focuses on type approval testing of the functioning of a radio apparatus but the functioning of radio apparatus is of course tested in many other contexts as well, e.g. during product development, manufacture, repair and service. In addition, the invention is applicable even during normal use of the radio apparatus.
New digital radio apparatus (digital mobile phones, for example) intended for operation in public data communication networks are tested for type approval prior to being introduced into the market. The equipment and methods used in the testing are usually defined in data communication network standards. FIG. 1 illustrates a known test arrangement in which testing is directed to a mobile station (MS) 101 of a cellular radio system. The mobile station may also be called user equipment (UE). A simulation system (SS) 102 simulates a cellular radio system during the test. Testing the functioning of data communication requires an active data link 103 between the SS and MS, which may be a radio link or a wire link through a testing interface at the mobile station.
Tests usually employ a technique in which a mobile station receives a downlink frame from the SS and sends back to the SS a corresponding uplink frame which contains the equivalent number of bits. The mobile station may even recycle to the SS the same individual bits that it received in the downlink direction. The SS examines whether the transfer of data or the operation of the mobile station have caused errors in the frame. Arrow 104 depicts the loopback. The arrangement has been suitable for testing the mobile stations of known cellular radio systems since in the known systems the data link capacity has been distributed symmetrically: the capacities of uplink and downlink data communication have been equal. In mobile stations of new cellular radio systems, however, it is necessary to test functions that involve asymmetric distribution of data communication capacity between uplink and downlink data communication. For instance, in functions relating to the browsing of information networks the downlink data communication capacity may be manyfold compared to the uplink capacity. The arrangement according to the prior art will then not work because all the bits of the received downlink frames will not fit in the uplink frames. In addition, mobile stations of new cellular radio systems may include functions based on unidirectional downlink data communication the testing of which naturally is impossible using the method according to the prior art.
From an earlier Finnish patent application no. 981267 by the applicant, which application has not become public by the priority date of this present application, it is known an alternative testing procedure suitable for the testing of data communication arrangements with asymmetric capacities. In said procedure a mobile station selects from tie bits of the downlink frame only a portion which is looped back to the uplink frames. The disadvantage of such an arrangement is that errors in those bits of the downlink frame that are not looped back uplink will remain undetected. In addition, this arrangement, too, is unsuitable for testing unidirectional downlink data communication links.
An object of the present invention is to provide a method for testing the functioning of a digital radio apparatus, which method is also suitable for testing the functioning of data communication arrangements which have asymmetric capacities or are unidirectional. Another object of the invention is that the method according to the invention can also be utilized in conjunction with the normal use of the digital radio apparatus.
The objects of the invention are achieved by including in the digital radio apparatus tested a circuit that can produce a copy of the test data used in the test. Thereby, error statistics can be compiled at the digital radio apparatus tested so that only the statistical results need be transmitted uplink. The uplink connection can be entirely separate from the downlink connection.
The method according to the invention is characterized in that it is comprised of steps wherein
a test signal is received in the downlink direction,
the test signal received is compared with a known form of the test signal,
information produced by the comparison about errors detected in the received test signal is stored, and
a signal representing the information stored is sent uplink.
The invention is also directed to a mobile station of a cellular radio system, characterized in that it comprises means for comparing a received signal to a known form of the signal and for storing the information produced by such comparison and for sending it uplink, which information represents errors detected in the received test signal.
In order to test functions relating to data communications the simulation system produces a pseudorandom bit sequence or other test sequence which is packed into downlink frames and sent to a mobile station. In accordance with the invention a circuit is included in the mobile station which is capable of producing the same test sequence as the simulation system. Thus the mobile station receiving downlink test data knows bit by bit what the received test data frames should contain. By comparing the received bit sequence to the sequence it has produced itself it can detect errors in the received sequence and compile various error statistics in the form of bit error ratio (BER) or frame erasure ratio (FER), for example. The uplink connection is only needed to convey these statistics to the simulation system, so that at best the need for uplink data transmission is only a fraction of the need for downlink data transmission. In general it can be said that the mobile station performs an error analysis of the received bit sequence using a bit sequence produced by the mobile station itself and sends to the simulation system information about the results obtained from the analysis.
The uplink data connection need not be associated with the downlink data connection at all. A so-called Bluetooth link has been proposed for new electronic apparatus to provide a short-range wireless data link between at least two apparatus. A mobile station can send information about the analysis results to the test equipment via the Bluetooth link.
The bit sequence generator and comparator circuit according to the invention may also be used when a mobile station is used in the normal manner as a mobile communication device in a cellular radio system. In many cases it is advantageous if the mobile phone or other such mobile station of a cellular radio system is able to examine the amount of errors in data received from a given base station. To perform such a measurement a base station may send a pseudorandom bit sequence such that the mobile station is able to produce the same sequence by means of its own generator and make the necessary comparisons in order to detect and record the errors that occurred in the downlink data transmission. Such a measurement may be applied e.g. to determine the strength of channel coding in the downlink transmission or in connection with a handover in order to find the best possible new base station.
The invention does not in any way limit the amount of error data sent uplink by the mobile station. According to an embodiment of the invention a great number of mobile stations can during normal operation compile statistics of errors detected in the downlink data transmission in connection with the operation of the mobile station and send corresponding data via base stations to fixed parts in the cellular radio system. If data are sent uplink relatively seldom their transmission will not take up a considerable portion of the data communication capacity available. At certain points of the network these data can be collected and combined e.g. with the information about the geographical locations of base stations, thus realizing automatic and continuous monitoring of the quality of service provided by the network. The network operator may use these data in network development, for example, so as to enhance network coverage.